These are the website you can visit to get more information about the Counting Principles.

Combinations and Permutations
Pierce, Rod. (2010, February 5). Combinations and permutations. Retrieved from http://www.mathsisfun.com/combinatorics/combinations-permutations.html

Dr. Math, . (2010).
Permutations and combinations. Retrieved from http://mathforum.org/dr.math/faq/faq.comb.perm.html

Spector, L. (2007).
Factorial. Retrieved from http://www.themathpage.com/aPreCalc/permutations-combinations.htm#Pfactorial

Definition and Examples
Omega, M. (2008).
Date interpretation and probability. Retrieved from http://www.omegamath.com/Data/d2.2.html

Pascal's Triangle
Webb, P. (2007).
Probability theory. Retrieved from http://www.probabilitytheory.info/topics/pascal_combinations_permutations.htm

Nachicharde, . (2008).
Computer permutations using pascal's tringle. Retrieved from http://www.scribd.com/doc/3902414/Compute-Permutation-Using-Pascal-Triangle

Counting Methods
Union County College, . (n.d.).
Counting methods. Retrieved from http://www.ucc.edu/NR/rdonlyres/D55520DE-CD3A-42CB-8CEE-471329AA6A91/0/CountingMethods.pdf

A Short History of Probability
Apostol, T. (1969).
A Short history of probability. Retrieved from http://www.cc.gatech.edu/classes/cs6751_97_winter/Topics/stat-meas/probHist.html